In earlier papers some proposals were made concerning experiments that could lead to the determination of the velocity of the gravitational interaction. This paper points out that this determination can only be achieved by measuring the delayed gravitational field and not by measuring the propagation velocity of gravitational radiation, which remains a controversial problem, both theoretically and experimentally. The possibility is shown of the existence of a gravitational effect not unlike the Poynting-Robertson light effect and the importance is discussed of its determination for space and astronomical research. Some of the proposed mechanisms for explaining the gravitational interaction are reviewed and their nonviability is objectively pointed out. Finally, conclusions are drawn as to the necessity of carrying out experiments to determine the velocity of the gravitational interaction.